In view of the mixed aggregate filling mine，in order to determine the optimum proportion of filling slurry, firstly，the physicochemical properties of filling materials were analyzed. Based on the theory of Talbol grading and the theory of maximum bulk density，the ratio of rod grinding sand and waste rock was determined. 13 groups of tests were designed with BBD response surface method（RSM-BBD） to analyze the effects of slurry mass fraction, cement-aggregate ratio and mixture aggregate ratio on the strength of filling body. Finally，the response surface model was constructed with the intensity of each age as the response value to study the correlation between each response parameter and the target response as well as the optimal ratio of the filling slurry under multi-objective conditions. The results show that the strength of the filling body is affected by single factors, and the interaction between the various factors has a great influence on the filling body. The interaction between the mass fraction and aggregate ratio plays a decisive role in the early strength of the filling body. The interaction between the cement-aggregate ratio and aggregate ratio has a significant effect on the medium strength of the filling body. The late strength of the backfill is greatly affected by the interaction of the mass fraction and cement-aggregate ratio. The optimization is based on the lowest unit filling cost, and the optimal ratio is as follow: slurry mass fraction is 80%, cement-aggregate is 1 ∶ 6，the ratio of rod grinding sand and waste rock is 3 ∶ 7，and the test is verified to meet Jinchuan Mine strength requirements.